Variable air-intake carburettor



Nov. 7, 1967 J. E. SIMOQET ETAL 3,351,327.

VARIABLE AIR-INTAKE CARBURET'I'OR Filed June 5, 1964 5 Sheets-Shet 1 lmhm Jame/ 7? fi'Lsfvwovvef d 7 fi'l e Nov. 7, 1967 I J. E. L. SIMONET ETAL 3,351,327

VARIABLE AIR- INTAKE CA'RBURETTOR Filed June 5, 1964 5 Sheeis-Sheet 5 Fig.-'4 I Y S 5 I 32 16 51 v E27 s 9 I I FfgJS J d)? fl Q) Nov. 7, 1967 J. E. L. SIMONET ETAL 3,351,327

VARIABLE AIR-INTAKE CARBURETTOR N 7, 1967 J. E. L. SIMONET ETAL 3,351,327

VARIABLE AIR-INTAKE CARBURETTOR Filed June 5, 1964 5 Sheets-Sheet 5 A? v 0 w a o Y I IIIIII United States Patent Office 3,351,327 Patented Nov. 7, 1967 7,46 8 Claims. (Cl. 261-48) ABSTRACT OF THE DISCLOSURE A variable air-intake carburetor having separate air inlet ducts feeding into the carburation chamber and including pressure responsive control means to vary the effective cross-section of said air inlet ducts, one of said ducts including a fuel inlet orifice fed by fuel inlet means also controlled by said pressure responsive control means.

This invention relates to a variable air-intake carburettor for internal combustion engines.

Conventional carburettors in which the air duct has a constant cross-section have the well-known drawback described hereunder:

If the flow cross-section for the air is chosen so as to be sufficiently large to ensure a proper supply to the engine at high power levels, the atomisation is poor at low power levels because the velocity of the air at the spraying point is too low and the power developed by the engine reduced owing to bad combustion. If, on the other hand, this cross-section is chosen so as to be sufiiciently small to ensure good atomisation at low power levels, at high power levels the air undergoes a loss of pressure which results in a reduction of the feeding rate of the engine and, consequently, a reduction in the maximum power.

In practice, the cross-section chosen is a compromise between a value which would result in loss of engine power at low power levels and one which would result in reduction of the maximum power.

To avoid this drawback, it is possible to construct a two-body carburettor, the two bodies of which function in succession, but these carburettors are complicated and their cost is high. Moreover, the change from operation on one body to operation on two bodies is never fully satisfactory.

Likewise, use is made of variable air-intake carburettors comprising, for varying the flow cross-section for the air, a plug fast with a piston or with a diaphragm which is subjected to the vacuum prevailing in the vicinity of the spraying point and which is displaced at right angles to the direction of flow of the air. A profiled needle con' nection to the plug adjusts the fuel-flow orifice which is located at the spraying point. The plug, however, rubs in its seat and consequently its movements are insufficiently precise. Moreover, it can only move vertically and not horizontally, so that it cannot be applied to a carburetor with a vertical air duct. Furthermore, it is difiicult to centre the metering needle correctly in its seat, so that the rate of the fuel-flow is not sufficiently accurate.

The carburettor according to the invention does not exhibit the aforesaid drawbacks. It is characterized in that a pressure-sensitive device which is actuable by the vacuum prevailing in the carburation chamber simultaneously controls a movable upstream air shutter, which controls a main air duct of the said carburation chamber, and a device which varies the useful cross-section of a metering duct for fuel supplied to a secondary air duct of the said carburation chamber.

The advantages of a carburettor constructed in this way will be clear from the following description of one form of carburettor constructed according to the invention.

This description, which is given with reference to the accompanying drawings and by way of nonlimitative example only, will make clearly understood how the invention can be carried into effect, the details appearing both from the text and from the drawings forming part of the said invention.

In the drawings the several figures show the various parts of the carburettor constructed according to the invention. In the drawings:

FIGURE 1 is a plan view of the carburettor according to the invention with the top cover removed;

FIGURE 2 is a rear view of the carburettor, partially in section on the line II-II of FIGURE 1;

FIGURE 3 is a vertical section on the line IIIIII of FIGURE 1;

FIGURE 4 is a vertical section on the line IVIV of FIGURE 1;

FIGURE 5 is a partial vertical section on the line V-V of FIGURE 4;

FIGURE 6 is a developed section showing the connection between the carburation chamber and the variablepressure chamber;

FIGURE 7 is a developed section showing the arrange- .ment of the auxiliary starter carburettor;

FIGURE 8 shows a modified constructional form of the strangulation device shown in FIGURE 6.

Referring to the drawings, in FIGURES 1, 3 and 6,

the reference 19 designates an air duct which will be referred to hereinafter as the main air duct and the references 23 and 21 designate, respectively, an upstream shutter and a downstream shutter which are disposed in the main duct 19 and are both capable of closing it to a greater or lesser degree according to their positions.

The shutter 21, the pivot spindle of which is designated by the reference 80, may be controlled by, for example,

the accelerator of a motor vehicle. In this case it is generally referred to as a butterfly valve. The space 20 between the two shutters 23 and 21 will be referred to hereinafter as the carburation chamber.

Into the carburation chamber 20 there opens an air duct 22, the mean cross-section of which is considerably smaller than that of the main duct 19 and may be, for instance, equal to A of the cross-section of the latter being for this reason referred to hereinafter as the secondary duct. In the secondary duct 22 there is disposed a fuel outlet orifice 35 to which fuel will be fed in a manner to be described hereinafter. In the constructional form shown, the secondary duct 22 is constituted by an upstream portion 22a parallel to the main duct 19 and a by a downstream portion 22b inclined with respect to the main duct 19, and the upstream end of the downstream portion 22b of the secondary duct 22 is formed by a frontal surface 11, the plane of which is inclined with respect to the main duct 19.

The upstream shutter 23 can pivot about a spindle 24 so as to close the main duct 19 to a greater or lesser degree.

In FIGURE 4, the reference 33 designates a chamber adapted to contain fuel and enclosing the known conventional elements which enable a constant fuel pres-' sure to be made to obtain therein. In the case of a liquid fuel such as petrol, for example, the chamber will be constructed as a constant level chamber. The constant level is shown in FIGURE 4 at 12. The chamber 33 is closed by a first cover 16 which is fixed to the chamber 33 by screws 14 (FIGURE 1) and which carries a tube 15 supplying the chamber 33 with fuel. An opening 18 is formed in the first cover 16. This opening is normally closed by a second cover 53. By' means of the second cover the needle to which reference will be made hereinafter and the lever which serves to displace it can be mounted one upon the other.

An inner part 64 is fixed to the first cover 16 by means of screws 17. The part 64 comprises a vertical'portion 64a enclosing a casing 57 in which there can slide the upper cylindrical portion 27b of a needle 27, the lower portion 27a of which is-profiled.

An annular space 30 is formed "between the vertical portion 64a of the inner part 64' and the casing 57 and the latter has ports 31 level with the annular space 30. Fuel contained in the chamber 33 reaches the ports 31 through the annular space '30.

Below the needle 27, the casing 57 has a calibrated orifice 25 into which the profiled portion 27a of the needle 27 can penetrate to a greater or lesser depth and which is therefore closed by the needle to a greater or lesser extent according to the position of the latter, so that the calibrated orifice 25 constitutes a metering duct for the fuel and the needle 27 constitutes a device for varying the useful cross-section of the metering duct 25. The needle 27 is shown in FIGURE 4 in its highest position, in which it almost completely closes the orifice 25, this position corresponding to slow running of the engine, as will be explained hereinafter.

. A channel 32 is formed partly in the inner part 64 and partly in the first cover 16. The channel 32 starts from the calibrated orifice 25 and the fuel which has passed through that part of the orifice 25 which has been left free by the needle 27 flows through it. The channel 32 constitutes a fuel duct conveying the fuel from the metering duct 25 to'the fuel-outlet orifice 35. At the orifice 35 an emulsion of fuel and air is formed.

In FIGURES l, 2 and 6, the reference 36 designates apparatus comprising a pressure-sensitive device. This apparatus is composed of the following elements: a base 37 having an orifice 38, a cap 39 mounted on the base 37, a diaphragm 40 inserted between the base 37 and the cap 39 and dividing the apparatus 36 into two chambers 41 and 42, the second chamber 42 of which communicates with the atmospheric air by means of the orifice 38, and a spring 43 which urges the diaphragm 40 towards the base 37. The chamber 41 communicates with the carburation chamber 20 through the conduit 44, so that the position of the pressure-sensitive device formed by the diaphragm 40 depends on the pressure obtaining in the carburation chamber 20.

In FIGURE 2 there will be seen a system for transmitting movement between the pressure-sensitive device 40 and the upstream shutter 23. The diaphragm 40 carries a rod 45 which is articulated by means of a pin 46 to a lever 47 fast with the pivot spindle 24 of the upstream shutter 23.

FIGURE 4 shows a portion of the movement transmission system between the pressure-sensitive diaphragm 40 and the needle 27. This transmission of movement is effected through the medium of the spindle 24 of the upstream shutter 23, so that the system for the transmission of movement between the pressure-sensitive diaphragm 40 and the needle 27 comprises the system described above for the transmission of movement between the diaphragm 40 and the upstream shutter 23'. The reference 48 designates a lever which is split at one of its ends and which, by means of a screw 49, grips the spindle 24. The lever is formed at its other end by a yoke, the two arms of which are joined by a pin 50. In this way, when the shifting of the diaphragm 40- causes the spindle 24 of the upstream shutter 23 to turn, the spindle 24 in turn causes the needle 27 to ascend or descend, being guided in this movement by the casing 57.

The carburettor which has just been described operates in the following. manner:

During operation of the engine: at slow running speed, the elements of the carburettor to which reference has been made in the foregoing are in the positions shown in FIGURES 1, 2, 3 and 4, that is to say the shutter 23 engine can be assumed to be effected wholly through the secondary duct 22 and the under-pressure or vacuum created in this duct by the velocity of the air causes fuel which has passed through the annular space between the needle 27 and the orifice 25 to gush into the orifice 35. The cross-section of the duct 22 can be chosen to be sufiiciently small for the velocity of the air in the secondary duct 22 to maintain a considerable value, thus ensuring effective atomisation of the fuel at 35.

Now if, by partly opening the downstream shutter 21,

the engine is called upon to supply greater power, the

vacuum in the carburation chamber 20, and consequently also in the chamber 41, increases and becomes sufficient to cause displacement of the movable diaphragm 40, and this results in opening of the upstream shutter 23 and displacement of the needle 27 in the direction to increase the useful cross-section of the fuel metering orifice 25. The opening of the upstream shutter 23 limits the increase of the vacuum in the carburation chamber 20 and this shutter assumes a position of equilibrium under the combined effect of the vacuum obtaining in the carburation chamber 20 and of the return spring 43. The flow of fuel is still supplied by the orifice 35, this flow increasing in proportion to the opening of the upstream shutter 23 as a result of the operation of the mechanical connection between this shutter and the needle 27.

When the engine is working at full power, the upstream shutter 23 is fully or almost fully open and the total crosssection of the main duct 19 and of the secondary duct 22 can be chosen to be sufficiently large for the induction loss due to the checking of the air as it passes through the carburettor to be very small.

It will be seen from the foregoing that the carburettor according to the invention reconciles the requirements of operation at full power with those of operation at low power.

The carburettor according to the invention may include a closing device which enables the secondary duct 22 to be closed upstream of the fuel outlet orifice 35.

This arrangement is illustrated in FIGURES 3 and 6, in which the closing device has a surface 66 adapted to be applied against the frontal surface 11 of the upstream end of the downstream portion 22b of the secondary duct 22 while the closing device is a slide valve 52 having a return spring 54 and formed by a movable wall of a chamber 55 which communicates with the carburation chamber 20 through a tube 56.

The effect of this arrangement is as follows:

When the engine is at a standstill there is no vacuum 1n the chamber 20 nor, consequently, in the chamber 55, and the spring 54 returns the slide valve 52 to its closed position shown in FIGURE 3. When the engine is driven by the starter, the vacuum created downstream of the downstream shutter 21 is transmitted to the fuel metermg orifice 25 anda flow of fuel is thus created which enables the engine to be started up. As soon as the engine is turning over under its own power at slow running speed, and therefore at a speed considerably higher than the driving speed produced by the starter, the increased vacuum obtaining in the carburation chamber 20 causes the displacement of the slide valve 52, which then uncovers the frontal surface 11, thus opening the secondary duct 22.

More generally speaking, the movement of the slide valve 52 can be controlled by a physical quantity which is dependent upon the rate of turning-over of the engine, in" such manner that the secondary duct 22 isclosed when the engine is at rest or is being driven at low speed, by the starter for example, and is partially or fully opened when the engine is turning at its normal slow running speed or at a higher speed.

To the fuel channel 32 (FIGURES 4 and 5) there can be connected a branch passage 51 capable of communicating with the atmospheric air, and an adjustable closing device 58, which is constituted in FIGURE 5 by a needlepointed screw and which enables this branch 51 to be closed to a greater or lesser extent.

This arrangement enables the fuel flow of carburettors which are mass-produced and which may differ slightly from one another to be adjusted once for all.

An air duct 60 (FIGURE 3) can connect the carburation chamber 20 to that portion of the main duct 19 which is located upstream of the upstream shutter 23 and to an adjustable closing device 61 which, in the construction shown in FIGURE 3, is constituted by a needlepointed screw and which enables this air duct 60 to be closed to a greater or lesser extent.

This device enables the richness of the mixture delivered at slow running speed to be adjusted.

The conduit 44 (FIGURE 6) connecting the variablepressure chamber 41 to the carburation chamber 20 may comprise a calibrated constriction 26.

The purpose of this arrangement is as follows:

The admission of fuel into the carburettor takes place with a certain inertia when the downstream shutter 21 is opened suddenly. A means of ensuring that the metering is nevertheless correct consists in delaying the opening of the upstream shutter 23, which is controlled by the vacuum appearing in the carburation chamber 20 at the instant of the sudden opening of the downstream shutter 21. The calibrated constriction 26 provides this delay.

This constriction operates in the two possible senses of the variation of the vacuum in the carburation chamber 20. The delay produced in closing the upstream shutter 23 when the downstream shutter 21 is reclosed rapidly causes an abnormal increase in the pressure in the carburation chamber 20, which may result in the stopping of the flow of fuel through the outlet orifice 35 and, consequently, the stalling of the engine.

To avoid this drawback, the conduit 44 may comprise, in place of a constriction 26 acting in both senses, a strangulation device which acts only when the pressure in the variable-pressure chamber decreases, that is to say when the upstream shutter 23 opens.

This strangulation device may be constituted (see FIG- URE 8) by a calibrated constriction element 70 inserted in the conduit 44 and by a branch duct 71 arranged in parallel with this calibrated constriction element 70 and containing a movable element 72 which closes the branch 71 only when the pressure in the variable-pressure chamber 41 decreases.

Alternatively the strangulation device may be constituted (see FIGURE 6) by a valve 28 inserted in the conduit 44, having a calibrated constriction 26, which valve occupies, when the pressure in the variable-pressure chamber 41 decreases, a closed position (the position illustrated) in which air is allowed to pass only through the calibrated constriction 26, but which, when the said pressure increases, occupies a position (the upper position, not shown) in which it allows air to pass through a passage 34 alternative to the calibrated constriction 26.

FIGURE 7 shows an auxiliary starter carburetor comprising in the usual manner the following elements: an air duct 65 opening into the main duct 19 downstream of the downstream shutter 21; a device 62 for forming a metered emulsion of fuel in air; a duct 63 conveying the emulsion into the air duct 65; a closing device 59 controlling both the air duct 65 and the duct 63 conveying the emulsion; and a lever 67 controlling the closing device 59. Lever 67 is manually opened during cranking. The reference 68 designates the orifice through which the fuel in the chamber 33 passes into the auxiliary carburetor and the reference 65a designates an orifice through which air is supplied to the auxiliary carburetor.

The special feature which is illustrated in FIGURE 7 is that the air duct 65 is controlled by the same closing device 52 which enables the secondary duct 22 to be closed.

This arrangement makes it possible to cause an increased vacuum to obtain in the air duct in order to enrich the mixture upon starting the engine.

The carburetor may also comprise a device by means of which the termination of the opening of the downstream shutter 21 will control the commencement of the opening of the upstream shutter 23.

This device is illustrated in FIGURE 2. In this figure, the spindle of the downstream shutter 21 carries a lever 81 on which pivots one of the ends of a connecting rod 82. The other end of the connecting rod 82 is articulated to a lever 83 mounted loosely on the spindle 24 of the upstream shutter 23. The lever 47 carries a bent lug 47a. When the spindle 80 turns, carrying with it the downstream shutter 21 in the opening direction and the lever 81, the connecting rod 82 is carried downwardly and it carries the lever 83 with it in rotary movement. Towards the end of the opening movement of the downstream shutter 21, the lever 83 bears on the bent lug 47a of the lever 47 and thus causes the spindle 24 of the upstream shutter 23 to turn.

The advantage of the device is as follows:

When starting of the engine has become impossible because of an excess of fuel, it is necessary to dispose of this excess by supplying the engine with air free from fuel for a certain time. The arrangement which has just been mentioned provides this result in the following manner:

As the upstream shutter 23 is partly open, the vacuum in the carburetion chamber 20 does not reach a value sufficient to cause the flow of fuel through the orifice 35 when the engine is driven by its starter. In this way, air free from fuel is introduced into the engine.

In the drawings, the reference 14 designates fixing screws, the reference 69 a plug which closes the chamber 55 in air-tight fashion and the references 73 and 74 fitting plugs.

What is claimed is:

1. A variable air intake carburetor for internal combustion engines, comprising a carburetion chamber, main and secondary air ducts communicating with said carburetion chamber, a movable air control member in said main duct upstream of said carburetion chamber, a fuel inlet orifice in said secondary air duct, a metering duct for the controlled supply of fuel to said secondary air duct through said orifice, a device operable to vary the available cross-section of said metering duct, to control the supply of fuel, pressure-sensitive means responsive to pressure variation in said carburetion chamber, to control operation of said air control member and said fuel control device, and an obturating device to open and close said secondary duct upstream of said fuel inlet orifice, in response to pressure variation in said carburetion chamber.

2. A carburetor according to claim 1, wherein said obturating device comprises a spring-biased slide-valve piston which is exposed to the pressure in said carburation chamber so as to be movable in response to pressurevariations therein.

3. A carburetor according to claim 1, wherein said pressure-sensitive means includes a variable volume chamber having a movable wall, a pressure conduit connecting said variable-volume chamber with said carburation chamber, whereby said wall is movable in response to pressure-variation in said carburation chamber and means mechanically connecting said movable wall with said air control member to operate the latter.

4. A carburetor according to claim 1, wherein said obturating device is operable to open said secondary duct upstream of said fuel inlet orifice in response to pressure reduction in said carburetion chamber.

5. The, carburetor of claim 1, wherein said obturating device'is operative to open said secondary-duct in response to a first vacuum level existing in said carburetion'chamber and said pressure sensitive-means is operative to open said air control member in response to aflsecon'd vacuum le'vel existing in said chamber, said first vacuum level being' lower than said second vacuum level whereby in the starting of an engine said obturat'ing device becomes operative to open said secondary duct before said pressure sensitive means becomes operative to open said air control member.

6. In combination, a variable air int'ake carburetor for internal combustion engines and an' auxiliary starting carburctor, said variable air intake carburetor comprising a carburetion chamber, main and secondary air duct communicating' with said carburetion chamber, a movable air control member in said main duct upstream of said'carburation chamber, a fuel inlet orifi'c'e in said secondary air duct, a metering duct for' the controlled supply of fuel to said secondary air duct through said orifice, a device operable to vary the available cross-section of said metering duct, to control the supply of fuel, pressure-sensitive means responsive to pressure variation in. said carbura'tion chamber, to control operation of said air control member and said fuel control device, a flow duct' downstream of said carburetion chamber and a flow control member in said downstream flow duct, and said auxiliary star-ting carburetor including an air intake, a fuel intake and an outlet for fuel-air mixture opening into said downstream fio'w duct downstream of said flow control member, an obtur'ating device being provided to open and close said secondary duct upstream of said fuel supply orifice, in response to pressure variation in said carburation chamber, and to control simultaneously the air intake of said auxiliary carburetor.

7. A variable air-intake carburetor for internal combustion engines, comprising a carburetion chamber", a main air duct communicating with said carbu'r'etiojn chamber, a movable air control member in said main duct upstream of carburet'ion chamber, a secondary air duct cornmunicating with said carburetion chamber and; comprising an upstream portion which is parallel to said main duct and a downstream portion which is inclined relatively to said main duct, a fuel inlet orifice in saiddownstream portion, said downstream portion having a seating surface upstream thereof, lying in a plane inclined relatively to said rnain duct, an obtur'ating member actuated in response to carburet-ion chamber pressure and cooperating with said seating surface to open and close said secondary duct upstream of said fuel inlet orifice, a metering duct. for the controlled supply of fuel to said secondary air duct through said orifice, a device operable to vary the available cross section of said metering duct to control the supply of fuel, and pressuresensitive meansresponsive to pressure variation in said carburetion chamber to control operation of said air control member and said fuel control device.

8. A variable air-intake carburetor for internal combustion engines, comprising a carburetion chamber, main and secondary air duct communicating with said carburetion chamber, a movable air control member in said main duct upstream of said carburetion chamber, a fuel inlet orifice in said secondary air duct, a metering duct for the controlled supply of fuel to said secondary air duct through said orifice, a device operable to vary the available' cross section of said metering duct to control the supply offuel, a variable volume chamber having a movable wall, mechanical means for operatively connecting said movable wallwith said air control member and said fuel control device, a pressure conduit connecting said variable-volume chamber with said carburetion chamber, whereby said wall is movable in response to pressure variation in said carburetion chamber, a valve in said pressure conduit closable and openable in response to,- respectively, pressure-decrease and pressure-increase in said variable-volume chamber, said valve having a calibrated opening to allow restricted communication between said variable-volume chamber and said carburetion chamberwhen said valve is closed.

References Cited UNITED STATES PATENTS 1 ,761,569 6/1930 Kimball 261-48 1,824,852 9/1931 Weber.

2,082,293 6/1937 Linga 261-50 2,084,489 6/1937 Hess 261-121 2,365,910 12/1944 Shafi.

2,544,111 3/1951 Schneebeli 261-48 X 2,683,028 7/ 1954 Schneebeli 261-48 X 2,969,783 1/ 1961 Braun 261-39 2,988,345 6/1961 Kolbe et a1. 261-50 3,078,079 2/ 1963 Mick.

3,278,173 10/1966 Cook et a1 261-50 HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Examiner. 

1. A VARIABLE AIR INTAKE CARBURETOR FOR INTERNAL COMBUSTION ENGINES, COMPRISING A CARBURETOR CHAMBER, MAIN AND SECONDARY AIR DUCTS COMMUNICATING WITH SAID CARBURETION CHAMBER, A MOVABLE AIR CONTROL MEMBER IN SAID MAIN DUCT UPSTREAM OF SAID CARBURETION CHAMBER, A FUEL INLET ORIFICE IN SAID SECONDARY AIR DUCT, A METERING DUCT FOR THE CONTROLLED SUPPLY OF FUEL TO SAID SECONDARY AIR DUCT THROUGH SAID ORIFICE, A DEVICE OPERABLE TO VARY THE AVAILABLE CROSS-SECTION OF SAID METERING DUCT, TO CONTROL THE SUPPLY OF FUEL, PRESSURE-SENSITIVE MEANS RESPONSIVE TO PRESSURE VARIATION IN SAID CARBURETION CHAMBER, TO CONTROL OPERATION OF SAID AIR CONTROL MEMBER AND SAID FUEL CONTROL DEVICE, AND AN OBTURATING DEVICE TO OPEN AND CLOSE SAID SECONDARY DUCT UPSTREAM OF SAID FUEL INLET ORIFICE, IN RESPONSE TO PRESSURE VARIATION IN SAID CARBURETION CHAMBER. 